DESCRIPTION: (Applicant's Description) The St. Louis Breast Cancer Tissue Resource (STLBCTR) has been operational since the fall of 1993 and is one of four components (others are University of Miami, Miami, Florida; Fox Chase Cancer Center, Philadelphia, Pennsylvania; Kaiser Permanente Northwest Division, Portland, Oregon) of the Cooperative Breast Cancer Tissue Resource (CBCTR). The CBCTR provides clinical information (a minimum of five years follow-up) and archival tissue specimens from breast cancer cases collected from these four sections of the United States. 25 percent of CBCTR cases are from the STLBCTR. CBCTR materials are available to any qualified researcher and are primarily of interest for testing the prognostic value of breast cancer markers. CBCTR case information is organized in a searchable database that can be accessed via the internet. STLBCTR is currently comprised of collaborators from three medical centers (St. John's Mercy, St. Luke's, and Barnes/Jewish:Washington University) who provide, through their respective institutions, archival specimens and clinical information to be contributed to the CBCTR. The primary site for the STLBCTR is Washington University, where database development, management, and case distribution take place. We propose over the next five year period to continue the work of the St. Louis Project and participate in the combined efforts of the CBCTR group, namely we propose to carry out five Specific Aims which include: 1) For the next two years, we will concentrate on the further distribution of the archival breast cancer case materials to qualified researchers. 2) We will continue to maintain the STLBCTR databases. 3) We will continue efforts to inform the scientific community about the resource and solicit quality applications. 4) We will continue collaborative work with the Research Evaluation Panel (REP) of the CBCTR to: a) review applications for the use of archival tissues, b) provide tissues for approved applications, c) review and possibly revise the prioritization of uses for the remaining specimens, and 5) at the end of year two, we will assess the cases remaining in the Resource and develop an estimate of the cases that are expected to be requested for the next three years. If new case accrual is indicated by the CBCTR group the STLBCTR could potentially contribute 3,000 new cases.